PHY397K - NUCLEAR PHYSICS - 2

Transcription

1 PHY397K - NUCLEAR PHYSICS - 2 PHY397K - NUCLEAR PHYSICS Spring 2015, Unique numbers: RLM 5.116, TTH 12:30-2:00 pm Christina Markert Office: RLM: Phone: cmarkert@physics.utexas.edu 1

2 Elementary Particles Summary 2

3 Particle Production 1 Billion o K 1 Trillion o K Start with light particles, no strong nuclear force 3

4 Particle Production 1 Billion o K 1 Trillion o K Previous Plot Now add hadrons = feel strong nuclear force 4

5 Particle Production 1 Billion o K 1 Trillion o K Previous Plots Keep adding more hadrons. 5

6 Hadrons and their Masses Theory: Quantum Chromo Dynamics The fundamental problem: how is baryonic mass generated Based on quark interactions ( MeV/c 2 )? 6

7 Analogies and differences between QED and QCD to study structure of an atom separate constituents electron nucleus neutral atom Confinement: fundamental & crucial (but not understood!) feature of strong force - colored objects (quarks) have energy in normal vacuum quark-antiquark pair created from vacuum quark quarks u,d, (s,c,t,b) white proton (baryon) (confined quarks) Strong color field white π 0 (meson) Force white grows proton with separation (confined!!! quarks) 7

8 High Energy and Heavy Ion Physics High energy physics: Study of the constituents of matter and the nature of interactions between them. Study single processes Accelerator: e + + e -, p+p, anti-p +p, Heavy ion physics: Study collective effects and medium properties of nuclear matter Accelerator: A+A, reference data are p+p, p+a, The main features of Quantum Chromodynamics (QCD) Confinement At large distances the effective coupling between quarks is large, resulting in confinement. Free quarks are not observed in nature. Asymptotic freedom At short distances the effective coupling between quarks decreases logarithmically. Under such conditions quarks and gluons appear to be quasi-free. (Hidden) chiral symmetry Connected with the quark masses When confined quarks have a large dynamical mass - constituent mass In the small coupling limit (some) quarks have small mass - current mass 8

9 Hadron Mass In vacuum: - asymptotically free quarks have current mass - confined quarks have constituent mass - baryonic mass is sum of valence quark constituent masses Masses can be computed as a function of the evolving coupling Strength or the level of asymptotic freedom, i.e. dynamic masses.

10 Generating a Deconfined State Present understanding of Quantum Chromodynamics (QCD) heating compression à deconfined matter! Quark Hadronic Nuclear Gluon Matter Plasma deconfined (confined)! 10

11 Generating a deconfined state (QGP) RHIC Present understanding of Quantum Chromodynamics (QCD) heating + compression à deconfined matter! SPS LHC Temperature Lattice QCD shows a rapid increase in the entropy associated with the deconfinement of quarks and gluons. à Critical temperature (phase transition) Tc = 173 MeV

12 Phase Diagram of Nuclear Matter Temperature ~150 MeV LHC RHIC SPS q q q q q q q q q q q q q q q q q q q q q q hadrons quarks and gluons hadrons AGS Center of mass energies: for different accelerators AGS: s ~ 5 GeV SPS : s ~ 17 GeV RHIC: s ~ 200 GeV LHC: s ~ 5500 GeV 12

13 Study all phases of a heavy ion collision If the Quark Gluon Plasma was formed, it will only live for s!!!! Nuclei are so thin because of velocity = nearly speed of light 13

14 Phase transition in collisions (time vs space) collider lab frame Detector QGP only lives ~ seconds Chemical freeze-out (Tch Tc): inelastic scattering ceases Kinetic freeze-out (Tfo Tch): elastic scattering ceases Christina Markert, UT Austin UT Austin, 14

15 Large Hadron Collider (LHC) c, or about 3 meters per second slower than the speed of light (c) speed = 11,000 revolutions per second 27 km circumference, m underground p+p collisions: s = 0.9, 2.36, 2.76, 7, 14 TeV Pb+Pb collisions: s NN = 2.76, 5.5 TeV 1 month per year (November 2010, 2011 ) Christina Markert, UT Austin UT Austin, 15

16 ALICE detector Drift Pixel